C :: Wrong Result In Integer Conversion To Little Endian

I am trying to convert uint32_t or unit16_t to chars in little endian. When I was reading the char s from binary file I used memcpy so I did not need to convert them, but now I try this:

Code:

static void write2Bytes(unsigned char ** pDestStr, uint16_t* item) {
(*pDestStr)[0] = ((uint16_t) item & 0x00ff);
(*pDestStr)[1] = ((uint16_t) item & 0xff00) >> 8;
*pDestStr+=2;


[code]...

In the last function I try either to cast to uint_32_t or unsigned char but in both case I got wrong values. The original binary string read from left: 0x36000003 (it is number corresponding to 48Mbytes).

And the result when casting to unsigned char is T000000 and T(>00 for uint_32. So what's wrong? I need to get some string with will be corresponding to 0x36000003. does this kind of convertion take a lot of compute performance when I one would use it offten (like when one would do convesions for bitmaps).